With the continuous development of the integrated circuit (IC) manufacturing technology, the critical dimension (CD) of ICs has been continuously reduced. When the CD of ICs is reduced to a same order as the exposure wavelength of the photolithography apparatus, an optical proximity effect (OPE) occurs. Such a phenomenon is caused by the diffraction and interference of the exposure light when the exposure light passes through a mask during the photolithography process. The diffraction and interference of the exposure light cause the deformation and distortion of the structure (or contours) of patterns of the IC when the patterns are transferred from the mask to a photoresist layer on a wafer.
To overcome the optical proximity effect, an optical proximity correction (OPC) method is often used. The OPC method pre-corrects the expected deformation and distortion of the mask patterns to cause the correction compensation value to be able to compensate the optical proximity effect generated by the exposure system of the photolithography apparatus. Accordingly, the final patterns formed on a wafer are identical to the target patterns.
The OPC method is able to correct the edge placement error (EPE) between the exposure patterns on a silicon wafer and the target patterns by multiple iterating steps. However, the OPC method is unable to correct the conflicting errors caused by the design. The conflicting errors refer to that correcting one error increases the error of other adjacent patterns. Such conflicting errors are unable to be solved simultaneously.
Thus, there is a need to develop a method that is able to solve the issue caused by conflicting errors. The disclosed methods and masks are directed to solve such an issue and other problems in the art.